A typical broadband loudspeaker system usually includes separate loudspeakers for providing the different frequency components of the broadband acoustic signal. These separate loudspeakers are coupled together by a suitable crossover network for applying the appropriate frequency component of the electrical input drive signal to each of the loudspeakers.
Usually, these types of speaker systems have more than one driver (i.e. a midrange and tweeter) that operate within at least a portion of the same frequency range. When two of these drivers operate within that range, destructive interference, which is also often referred to as phase discontinuity, in the axial response can arise caused by the cancellation of the spaced-apart like sound waves generated by each component.
Because of the finite distance between the two drivers, the sound waves will have a phase discontinuity. At points in space located axially about the speaker system, the two sound waves will sum or subtract from each other causing the net audio signal at that frequency to be muted or accentuated. This is commonly referred to as lobing and is shown schematically in prior art FIG. 5B.
More recently, speakers having dual, spaced-apart, in plane, drivers that operate within the same frequency range are gaining in popularity, particularly for use as auxiliary computer speakers. However, one side effect of having dual, spaced-apart, in-plane drivers is that they will acoustically interfere with each other over a much broader frequency range when operated together.
Efforts to reduce or prevent this interference have had limited success. For example, U.S. Pat. No. 4,233,472 to Kleis, the disclosure of which is hereby incorporated by reference, disclosures connecting more than two in-plane drivers together in series with some of the drivers being mutable at defined frequencies as a result of low pass filtering. While such structures reduce some interference, it relies on more than two drivers with at least two of the drivers being positioned at an angle with respect to each other. Such a configuration is not desirable in many speaker applications, including use as auxiliary computer speakers, which favor having only two, spaced apart, in-plane drivers in each speaker.